Conventional cargo systems typically include various tracks and rollers. For example, an aircraft cargo system may span a length of an aircraft and may be configured to load and unload aircraft cargo. Power drive units (“PDUs”) convey cargo forward and aft along the aircraft on conveyance rollers which are attached to the aircraft floor structure. For example, cargo may be loaded from an aft position on an aircraft and conducted on a unit load device (“ULD”) or a pallet by the cargo system to a forward position and/or, depending upon aircraft configuration, cargo may be loaded from a forward position on an aircraft and conducted by the cargo system to an aft position. Power drive units can be configured to raise and lower to selectively engage and drive/propel a unit load device in a desired direction over a cargo deck's roller elements.